A micromachined double lumen microdialysis probe connector with incorporated sensor for on-line sampling

In this paper, a micromachined double lumen microdialysis probe connector for on-line, in-vivo sampling is presented. The connector forms an integral part of a double lumen type microdialysis probe and guides the flow of sample fluid (‘dialysate’) directly into a flow cell with space for integrated sensors. Basically, the connector is a sandwich construction of two, multistep KOH etched silicon wafers which, after bonding allows the easy insertion of two concentric fused silica capillaries, required to construct the probe. For the experimental evaluation of the performance, in this work, a chloride selective sensor was integrated in the flow cell of the connector to continuously measure the chloride concentration in the dialysate flow. It will be shown that by adopting micromachining techniques, the induced lag time of the measurement can easily be decreased by a factor of more than 5, as compared to a conventional probe connected to a flow-through sensor. Another benefit of the proposed direct coupling of double lumen microdialysis probes and microfluidic structures in silicon, is the fact that all critical fluidic connections, especially the probe/sensor connection, are kept inside, making the microanalysis system more rigid.